Asphalt shingle cracks

Thanks Gary.

Interesting “narrative” from that thread.

You say less than a year old…is it possible that they were installed in Feb or March? The adhesive strips may have not had a chance to adhere to the bottom tabs (lack of warmth/sun). A good storm/wind may have contributed to the tearing.

Here is some good info on cold weather installs…

PDF

Jeff

Close.

  1. The shingles are installed when they’re in a hot and expanded condition. The adhesive strip is strong and bonds fully and shingles are well nailed down.

  2. A very cold night comes along and shingles all contract.
    Contraction is so extreme that either the adhesive strip bond has to break to relieve the tension, or is the strength of the adhesive bond exceeds the tensile strength of the shingle, and the tension is relieved by splitting of the shingle above the joints between shingles in the course below.
    That’s why you see splits in the shingles above joints.

Kenton, thanks for explanation, makes a lot of sense.

The roof in question on this thread had both vertical and horizontal “hairline” cracks. Could installing over uneven surface, and/or multiple layers, factor in?

Horizontal cracks can be from contraction of the roof sheathing, although it expands and contracts more with fluctuations in moisture content than with temperature.

This seems to be the best explanation. I’ve installed many, many roofs through the years, and it does appear to be careless handling by the installers. Just my opinion.

The stair-step pattern is a major clue for splitting above joints, which would caused by contraction after the adhesive strip has bonded. Horizontal splitting or cracking could easily be wind-caused if a roofing contractor were dumb enough to install them in a high wind. Wind-caused horizontal splits or cracks should appear an inch or so below the butts of the shingles in the course above
They wouldn’t be that dumb would they?

Actually they would Kenton! Last week I saw roofers doing a Hotel with air compressor and nailer. The wind was about 20 mph that day. They were using the bundles to hold down the ends. The roof was low slope also and they where using conventional architectural shingles.
Cha Ching cha ching.
One more thing is it was cold and light snow had just fallen.